The first proper, official mention of the Time War comes during the novelization of 'Remembrance of the Daleks', when the Special Weapons Dalek recalls fighting in "the time campaign, the war to end all wars". This carries with it the interesting implication that for the Imperial Dalek faction at least, the Time War has (in part, at least) already happened. Meaning that perhaps this is the incident that Dalek Caan rescued Davros from...and the Seventh Doctor is participating in events out of synch with the Gallifreyan timestream. (Which is strangely in keeping with the Seventh Doctor's persona...)
It also confirms my general belief that the novelization of 'Remembrance' is actually the starting point for the 2005 series, conceptually if not actually. Which, in turn, confirms my general belief that Ben Aaronovitch is freaking metal.